Recently, as information has been rapidly digitalized, copyright of digital content becomes important. In general, unlike analogue content, since digital content can be unlimitedly copied without a loss of information, the digital content can be easily exposed to illegal copy and use. Accordingly, a content protection technique capable of safely protecting digital content against illegal copy and use has to be supported in order to provide a digital content service.
A digital rights management (DRM) is a total digital content protection technique capable of allowing only a legally authorized user to use digital content. The DRM provides the total protection framework for distribution of the digital content. For example, digital content is transformed into encrypted data in a package form by using an encryption technique. The digital content cannot be used without a legal authentication process.
The DRM becomes bases of a secured and legal content service in linkage with various content service models. In practice, current content service providers employ DRMs unique to the current content service providers to protect content provided by the current content service providers. For example, in case of a sound source service for providing sound sources through on-line, sound sources that are encrypted as a predetermined encryption pattern are provided so as to prevent illegal copy. The sound sources are reproducible by using only an application provided by the service provider. Accordingly, the user purchases the sound sources from a service provider and reproduces the sound sources by using a device such as a personal computer (PC), a mobile phone, an MP3 player, and the like, in which the application provided by the service provider is installed.
However, since the DRM has technical and political closure properties, different DRMs are not compatible with one another, in general. Accordingly, although the DRM content service has advantages in security and legality as compared with a general content service, the DRM content service has disadvantages in that the usage of the content is limited and inconvenient. The aforementioned problem deteriorates flexibility of a distribution structure of digital contents. Finally, the problem prevents activation of a market of digital content services.
Recently, a DRM interoperable system that provides a interoperable framework in which different DRMs are compatible with one another is suggested.
The DRM interoperable systems commonly employ a concept of a domain as a basic unit of a DRM trusted framework. The domain may indicate a set of authenticated devices or a set of software systems. It is possible for devices or software systems (hereinafter, collectively referred to as devices) which are authenticated in the domain through a predetermined procedure to share contents with the same DRM or different DRMs within an allowed area.
The DRM interoperable system may be constructed by defining functions of entities based on an environment in which the entities that construct the domain physically interact with one another and by suitably linking the entities with one another.
However, in the past, non-compliant content which is not supported by the DRM interoperable system exist. Since the non-compliant content is not supported by the DRM interoperable system, it is impossible to share the non-compliant content in the DRM interoperable system. That is, the non-compliant content may be in contraposition to non-compliant content which can be supported by the DRM interoperable system.
Non-compliant contents may be classified into clean contents and non-clean contents.
The clean contents may indicate original contents which are not encrypted or scrambled. Since the clean contents are not applied with a DRM, there is no rights information therein, in most cases. Accordingly, it is possible to limitlessly use the contents, and however, the contents cannot be protected.
Although the non-clean contents are encrypted or scrambled, the non-clean contents may indicate DRM contents which are not supported by the DRM domain service. Although rights information for using the non-clean contents may exist, the rights information does not satisfy rights information used in the domain, and accordingly, it is impossible to provide the DRM domain service to the non-clean contents. For example, sound sources stored in a compact disc (CD) are scrambled so as to prevent illegal copy. A copy rights may be assigned through a managed copy. However, a method of applying the copy rights to the DRM domain service is not prepared.
The clean contents or non-clean contents may occupy most parts of currently distributed contents. However, in the past, contents supported by the DRM interoperable system, are limited to compliant contents. Accordingly, a plurality of contents are not supported by the DRM domain service. This problem becomes one of important factors which delay popularization and commercialization of the DRM domain service. Accordingly, a method and base system for supporting the non-compliant contents are required to be developed.